This call of the trail is something that is stronger than anything else in Muller’s mentality, and now and then it brings him into conflict with the department, ... or with his own better nature.  Sometimes his unerring instinct discovers secrets in high places, secrets which the Police Department is bidden to hush up and leave untouched.  Muller is then taken off the case, and left idle for a while if he persists in his opinion as to the true facts.  And at other times, Muller’s own warm heart gets him into trouble.  He will track down his victim, driven by the power in his soul which is stronger than all volition; but when he has this victim in the net, he will sometimes discover him to be a much finer, better man than the other individual, whose wrong at this particular criminal’s hand set in motion the machinery of justice.  Several times that has happened to Muller, and each time his heart got the better of his professional instincts, of his practical common-sense, too, perhaps, ... at least as far as his own advancement was concerned, and he warned the victim, defeating his own work.  This peculiarity of Muller’s character caused his undoing at last, his official undoing that is, and compelled his retirement from the force.  But his advice is often sought unofficially by the Department, and to those who know, Muller’s hand can be seen in the unravelling of many a famous case.

The following stories are but a few of the many interesting cases that have come within the experience of this great detective.  But they give a fair portrayal of Muller’s peculiar method of working, his looking on himself as merely an humble member of the Department, and the comedy of his acting under “official orders” when the Department is in reality following out his directions.

THE CASE OF THE REGISTERED LETTER

by Grace Isabel Colbron and Augusta Groner

“Oh, sir, save him if you can—­save my poor nephew!  I know he is innocent!”

The little old lady sank back in her chair, gazing up at Commissioner von Riedau with tear-dimmed eyes full of helpless appeal.  The commissioner looked thoughtful.  “But the case is in the hands of the local authorities, Madam,” he answered gently, a strain of pity in his voice.  “I don’t exactly see how we could interfere.”

“But they believe Albert guilty!  They haven’t given him a chance!”

“He cannot be sentenced without sufficient proof of his guilt.”

“But the trial, the horrible trial—­it will kill him—­his heart is weak.  I thought—­I thought you might send some one—­some one of your detectives—­to find out the truth of the case.  You must have the best people here in Vienna.  Oh, my poor Albert—­”

Her voice died away in a suppressed sob, and she covered her face to keep back the tears.

The commissioner pressed a bell on his desk.  “Is Detective Joseph Muller anywhere about the building?” he asked of the attendant who appeared at the door.